In the field of tissue engineering, research has determined that the mechanical properties of a substrate to which cells attach mediate different aspects of cell function including attachment, proliferation, migration, and differentiation. As these effects can be very pronounced, it is imperative to determine the stiffness of soft materials used in tissue engineering. Numerous techniques are available for measuring the mechanical modulus of a material, each with distinct advantages and disadvantages for the field of tissue engineering.
For instance, shear rheometry can be used on macroscopic length scales for measurement of elastic and/or viscoelastic measurements. Gel points can be readily determined, and the technique provides an “average” response. However, material heterogeneities cannot be probed. Further, shear rheometry requires a relatively large amount of material, often not available or practical. Equipment set-up is expensive and requires considerable training.
Contact mechanical tests are, likewise, often employed for modulus measurements on length scales of cellular (i.e., mesoscopic) dimensions. However, as such techniques probe only surface properties, the resulting data is not representative of the bulk material. Again, equipment is expensive and requires considerable training.
Techniques such as microbead rheology can be used to probe microscopic length scales, and modulus measurements produce values similar to traditional rheology. However, such techniques are generally restricted to softer (<100 Pa) materials and the microbeads can disturb natural gel formation. Again, such techniques typically require training and expertise of the sort precluding routine laboratory applications.
All of the aforementioned techniques are complicated, require an undue amount of training, and can be extremely expensive. As a result, the search for an effective, cost-efficient method for material analysis remains an on-going concern in the art. One such approach involves cavitation and subsequent measurement of mechanical moduli. However, previous such techniques and related apparatus have been limited to surface energy analysis of liquids.